Interpretive Summary: Rates of energy expenditure (EE) are determined largely by body weight and body composition. Therefore, it is imperative to normalize or adjust rates of EE of growing children and adolescents for body weight or composition as part of the statistical analysis. In this study, we studied allometric or power function models for the normalization of EE data in a large sample of children (n=833), ages 5 to 19 y for a wide range of physical activities. Total EE, basal EE, sleeping EE, and cycling EE were measured during 24-h room calorimetry. Walking and maximal EE were measured using a treadmill protocol. We found that the appropriate exponents for normalizing EE by weight or composition were influenced primarily by the level of EE, with only minor effects of gender and weight status.

Technical Abstract:
The most appropriate model for normalization of energy expenditure (EE) data for body mass or composition in growing children and adolescents has not been studied extensively. In this study, we investigated allometric modeling for the normalization of EE data for body mass or composition in a large cohort of children (n=833), ages 5 to 19 y for a wide range of physical activities. Anthropometry was performed by standard techniques, and total body fat free mass (FFM) and fat mass (FM) were determined by dual-energy x-ray absorptiometry (DXA). Total energy expenditure (TEE), basal energy expenditure (BEE), sleeping energy expenditure (SEE), and cycling EE were measured during 24-h room respiration calorimetry. Walking and maximal EE (MaxEE) were measured according to a treadmill protocol. Allometric or power function models were used to identify appropriate scaling parameters for EE. For BEE and lower levels of EE, weight scaled to 0.5. For cycling and treadmill walking/running, the weight exponent approached 0.7. Scaling EE for FFM resulted in exponents of 0.6 for lower rates of EE and 0.8-1.0 for higher rates of EE. Appropriate scaling of EE for body weight and composition of children and adolescents varied primarily as a function of the level of EE. In some instances, the exponents for scaling EE by body weight or composition were influenced by gender and weight status, but not by age.